In general, DACs that use the BitShares brand share the common BitShares Toolkit which makes them increasingly interoperable in a common client environment. They use the DPOS security model, honor the BitShares Social Consensus and present a compatible brand image. This is an evolving industry, so exceptions to these rules may be considered on a case by case basis.
I think freetrade wanted to honor the pt/ags communities along with the others honored as a means to bring value and a supported userbase to his DAC.
As far as the initial question...I see BitShares as a technology that was meant to fix what bitcoin and proof of work fail to do. Proof of work burns energy which means you might make and secure a token, but that any infrastructure that accepts your token must do it out of the goodness of their hearts or for diversification purposes.
Using DPOS enables any Primary Currency DAC (for instance, btc, ltc, pc...etc) to redirect that money originally thrown at power companies into the construction of DACs that offer services redeemable in your coin.
In this way, while every pow coin out there is in a one way relationship with engrained power companies, DPOS coins derive value from the value of the services for which they are accepted.
If the world was my perfect vision...delegates would form partnerships with media outlets and "altcoins" with devs who are obviously competent (like ppc, drk...etc) and give a % of their fees to helping pay for the help they will need in order to build their ghost towns into thriving commerce hubs.
In return, the BitShares community also gets a stake in those coins DACs that come online, A) to honor the delegate(s) that helped them when they didnt have to...and B) to gain the support and future patronage of the BitShares community for those DAC services in the future.